Sains Malaysiana 47(1)(2018): 181–187
http://dx.doi.org/10.17576/jsm-2018-4701-21
Enhancement
of Thermoelectric Properties of Yb0.25Co4Sb12
Skutterudites through Ni Substitution
(Peningkatan
Sifat Termoelektrik bagi Bahan Skuterudit Yb0.25Co4Sb12 melalui Penggantian Ni)
MOHAMED BASHIR
ALI
BASHIR1,
SUHANA
MOHD
SAID2*, MOHD
FAIZUL
MOHD
SABRI2, YUZURU
MIYAZAKI3, DHAFER
ABDUL AMEER SHNAWAH2, MASANORI
SHIMADA3 & MOHAMED HAMID ELSHEIKH4
1Department
of Mechanical Engineering, Faculty of Engineering, Eldaein University,
63312 Eldaein, Sudan
2University of Malaya,
50603 Kuala Lumpur, Federal Territory, Malaysia
3Tohoku University, 2
Chome-1-1 Katahira, Aoba Ward, Sendai, Miyagi Prefecture 980-8577,
Japan
4R&D,
Cree Inc., Durham,
NC 27703, USA
Diserahkan: 28 November 2016/Diterima: 9 Jun 2017
ABSTRACT
In this work, we investigate the effects of Ni doping on the
thermoelectric (TE) properties of Yb0.25Co4Sb12 sample.
Yb0.25Co4-xNixSb12 (0 ≤ x ≤ 0.5) samples were prepared by mechanical alloying
and subsequently consolidated by spark plasma sintering. The morphology of
consolidated samples were characterized by X-ray
diffraction (XRD) and scanning electron microscopy and
energy-dispersive X-ray spectroscopy (SEM-EDS). The thermoelectric
properties of bulk samples were measured from room temperature to 800 K. The XRD analysis
confirmed that, the successful formation of the Co4Sb12 skutterudite
phase and Ni is substituted into Co site of the skutterudite crystal lattice.
Moreover, the electrical resistivity decreased to 14.6 μΩm at 785 K for Yb0.25Co3.5Ni0.5Sb12 sample,
due to increase of the electron concentration by Ni-addition. The absolute
Seebeck coefficient reached the highest value of 223 μV/K at 592 K for Yb0.25Co3.7Ni0.3Sb12 sample,
thus yielding a maximum value of power factor of 2.41 × 10-3 W/mK2 at
592 K. The highest dimensionless thermoelectric figure of merit value ZT of
0.49 at 692 K has been achieved for the Yb0.25Co3.7Ni0.3Sb12 sample,
compared to ZT=0.06 for the Yb0.25Co4Sb12 sample
at same temperature. This work indicates a strategy to improve the
thermoelectric performance by Ni substitution of Co sites in the Yb0.25Co4Sb12 skutterudite
through simultaneous improvement of its electrical conductivity, Seebeck
coefficient and reduction of its thermal conductivity.
Keywords: Mechanical alloying; Ni-doping; skutterudite;
thermoelectric
ABSTRAK
Dalam kajian ini, kesan pendopan Ni ke atas sifat
Yb0.25Co4Sb12
telah dikaji. Sampel
Yb0.25Co4-xNixSb12
(0 ≤ x ≤ 0.5) telah disediakan dengan kaedah
pengaloian mekanikal dan seterusnya digabungkan dengan pensinteran
pencucuh plasma. Morfologi untuk sampel
gabungan telah dicirikan oleh pembelauan sinar-X (XRD)
dan imbasan mikroskop elektron berserta tenaga serakan X-ray spektroskopi
(SEM-EDS).
Ciri termoelektrik sampel telah diukur daripada suhu bilik ke 800
K. Analisis XRD
mengesahkan bahawa Ni berjaya didopkan ke dalam Yb0.25Co4-xNixSb12
CoSb3
dalam fasa skutterudite, dengan Ni menggantikan beberapa
lokasi Co dalam kekisi kristal skuterudit. Selain itu, kerintangan
elektrik menurun kepada 14.6 μΩm di 785 K bagi sampel
Yb0.25Co3.5Ni0.5Sb12,
disebabkan oleh peningkatan bilangan pembawa cas elektron oleh Ni.
Pekali Seebeck mutlak mencapai nilai tertinggi 223 μV/K pada
592 K bagi sampel Yb0.25Co3.7Ni0.3Sb12
, lalu menghasilkan nilai maksimum faktor kuasa 2.41
× 10-3 W/MK2
pada 592 K. Angka merit, ZT yang optimum adalah 0.49 pada 692
K telah dicapai untuk sampel Yb0.25Co3.7Ni0.3Sb12.
Kajian ini menunjukkan strategi untuk meningkatkan
prestasi termoelektrik melalui penggantian Ni pada bahagian Co dalam
bahan skutterudite Yb0.25Co4Sb12,
sekaligus menambahbaik kekonduksian elektrik, pekali Seebeck dan
pengurangan kekonduksian haba.
Kata kunci: Ni-dop; pengaloian mekanikal; skuterudit;
termoelektrik
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*Pengarang
untuk surat-menyurat; email: smsaid@um.edu.my
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